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Why Bonobos Don’t Kill Each Other

Brian Hare, an assistant professor at the Duke Institute for Brain Sciences at Duke University, and Vanessa Woods, a research scientist in the Department of Evolutionary Anthropology at Duke, do comparative studies on the cognitive development of bonobo apes, chimpanzees and humans. Ms. Woods, 33, a former journalist from Australia, has just published a book about their marriage and work, "Bonobo Handshake: A Memoir of Love and Adventure in the Congo." We spoke last month after they had appeared at the World Science Festival in New York City. An edited version of the conversation follows:

Q. VANESSA, YOU’RE NOT A TRAINED PRIMATOLOGIST. HOW DID YOU COME TO WORK WITH BONOBOS?

A. Vanessa: By a series of happy accidents. For much of my 20s, I didn’t know what I wanted to do with my life. So I went to Africa and did a little of everything. I worked with chimpanzees for a bit and then I did a little bit of filming and I worked a bit on children’s books.

When I met Brian in 2004, I was 27 and volunteering at a chimp sanctuary in Uganda. Brian was testing the chimpanzees’ capacity for cooperation and sharing.

Then Brian got invited to the Congo to perform the same experiments on bonobos, our other close ape relations. Would I come along as a helpmate? I hated the idea. My mother, the world’s biggest feminist, always said, “Never follow a man — do your own thing.” I knew almost nothing about bonobos. I thought: “Aren’t those the apes that have a lot of sex?”

Brian: That’s what most people know about bonobos: they have a lot of sex. That’s not what’s interesting about them. The No. 1 reason they are interesting is that they don’t kill each other. The question I was in Africa chasing was: why will a chimp get into a severe fight with another — perhaps kill or maim it — while a bonobo, in the same situation, won’t? I’m basically an anthropologist. And in looking at the psychological and social propensities of our close relatives, learning about their differences in behavior, maybe we’ll be able to make some inferences about what happened during human evolution.

A. Brian: The type of experiments that developmental psychologists try on human subjects to see how they’d behave in certain situations. With the apes, I designed tests and games where they could obtain treats — apples, bananas — if they engaged in acts of cooperation.

The chimps, it turned out, would only cooperate if they were teamed up with others of equal status. If you put them with subordinate or superior status chimps, they became intolerant. When you had equal-status chimps together on a test, they were able to solve conflicts of interest, negotiate successfully and recruit collaborators. But when we changed one simple thing, we’d crush their ability to cooperate. We took separate piles of treats and combined them into one. Immediately, the chimpanzees started competing with each other and all cooperation fell apart.

Later, when we were in the Congo, we posed the same question to the bonobos. The piles of food were merged. No problem. Everyone shared. My doctoral thesis adviser at Harvard, Richard Wrangham, thinks this may be because chimpanzees evolved in a situation of food scarcity while bonobos developed in the giant salad bowl of the Congo basin where there was abundance.

Photo

TEAMWORK Brian Hare and Vanessa Woods at Duke University last month.Credit
Jeremy M. Lange for The New York Times

Vanessa: Another thing: bonobos are matriarchal. If it’s usual for female chimps to get pushed around and battered by males, bonobo females run things. Once, while in the Congo, I witnessed Tatango, this young male bonobo, start to do what the chimps in Uganda regularly did: he went up to the alpha female, Mimi, and backhanded her across the face. She gave him the most withering look. Within seconds, five unrelated females chased him into the forest. Poor guy. They almost took his testicles off. After that, he never made another problem. Bonobo females seem to know that if they stick together, the males can’t dominate.

Brian’s gender was actually a problem when we first arrived in the Congo. He walked right up to the bonobos, did all these loud displays, which usually fascinates chimpanzees and makes them want to play with you. The male bonobos were terrified of Brian and the female ones would have nothing to do with him. I had to run the experiments because they seemed to accept me more easily. Once that became clear, my role became larger than that of a “helpmate.” With time, the work became mine, too.

Q. WHERE EXACTLY DID YOU PERFORM THESE EXPERIMENTS? I’M UNDER THE IMPRESSION THAT BONOBOS ARE DIFFICULT TO RESEARCH BECAUSE THEIR HABITAT IS IN THE WILDS OF THE CENTRAL AFRICAN RAIN FOREST.

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A. Brian: Well, we went to the semiwild. There’s this amazing conservationist, Claudine Andre, who founded a sanctuary in Kinshasa for bonobos orphaned by the bush meat trade. She’d convinced the Congolese to let her use this 100-acre wood with lily ponds and forests that once had been a bucolic retreat for Mobutu Sese Seko.

Working with the orphans in the sanctuary, they were much more like wild animals than the captive bonobos one might study at a zoo. They were obviously much easier to see and interact with than animals in the forest.

Q. HAVE YOU FOUND ANSWERS TO THE SCIENTIFIC QUESTIONS YOU’VE BEEN ASKING?

A. Brian: Tentative answers. The research is ongoing. Some of the differences between chimps and bonobos have to do with what happens to them during their development. Essentially bonobos and chimps have similar behaviors as youngsters. Like bonobos, juvenile chimps are very tolerant, peaceful. When they go through puberty, they change. So what happens to adolescent bonobos? Nothing! They don’t change. Their levels of play, their levels of sharing and sex, it all keeps going. They are Peter Pans.

Q. HOW ENDANGERED ARE BONOBOS?

A. Vanessa: Very. There are probably about 10,000 remaining in the wild. Nobody really knows. It’s hard to get in there and count them all.

There’s very little agriculture in the Congo. And a lot of hunting. Bush meat is how people get their protein. And unfortunately, bonobos are really prized meat for hunters because they live in communities. If you’ve found one, you’ve found thirty that you can shoot and kill all at the same time. Of course, bonobos aren’t the answer to feeding the Congolese people. There are 68 million Congolese and 10,000 bonobos. The people need aid, some kind of agricultural program so that the farming becomes sustainable, and peace.